The present invention relates, according to an aspect thereof, to a method for controlling the engine temperature of a vehicle, especially a utility vehicle, such as a heavy duty vehicle or similar.
In order to obtain efficient working conditions in a vehicle engine the engine is provided with a cooling system. Normally the engine uses heat exchanger with a coolant liquid and an engine fan. The temperature of the cooling system is depended on the workload of the engine, wherein to avoid too high temperatures of the cooling fluid, the engine fan forces an airflow over the heat exchanger. Today the activation and control of the engine fan is controlled by a thermostat.
Especially in heavy utility vehicles the engine fan is a major power consumer, and thereby has a significant influence on the fuel efficiency of the vehicle. There are methods aiming to avoid a start of the engine fan. Said methods uses the auxiliary systems of the vehicle to draw heat from the engine during short periods, wherein an activation of an engine fan is delayed or avoided. However, these methods have the drawback that the purpose of said auxiliary systems is not always needed or wanted, such as heating of the driver's cabin.
The present invention aims, according to an aspect thereof, to solve the above mentioned problem and thereby suggest a method for controlling a drivetrain in a more efficient way.
The present invention rests, according to an aspect thereof, upon the finding, that an activation of an engine fan can be avoided, if the drivetrain of the vehicle is controlled in such a manner that the temperature of the engine and the cooling system is kept below a predetermined threshold value, which is dependent of an activation temperature of the engine fan.
Hence, the present invention, according to an aspect thereof, provides a method to control a drivetrain of a vehicle, especially a utility vehicle. The method is adapted for a drivetrain comprising an engine with a cooling system, said cooling system comprises an engine fan, wherein the cooling system and the drivetrain is controlled by an electronic control unit (ECU), and wherein said ECU having access to topographic data of an upcoming route, wherein said method comprises the steps of;                determining a topology of an upcoming route of the vehicle,        estimating the load of the engine dependent of the topology of the upcoming route,        estimating a temperature variation of the cooling system during the upcoming route, and        controlling the drivetrain dependent on the estimated temperature variation, such that an actual temperature of the cooling system is kept below a temperature threshold value during the upcoming route of the vehicle, andwherein said temperature threshold value is dependent on a temperature at which said fan is activated.        
The advantage with this method is that it reduces the number of times the cooling fan has to be activated to provide additional cooling and thereby reduce the energy needed to cool the engine. Hence when a topology of an upcoming route is determined, an estimation of the load of the engine during the upcoming route can be performed through an algorithm, considering the influencing factors, such as said topology of the upcoming route and the specification of the drivetrain. The ECU can get the information about the topology of the upcoming route from any available source, i.e. a navigation system, a digital map or a database with route information. The temperature variation can thereby also be estimated and peak temperatures where the engine fan is activated can be found. An amended drivetrain control strategy is thereby implemented, which keeps the engine and cooling system temperature below a temperature threshold value, at which the engine fan is activated. Fuel is saved because an activation of the high power consumer engine fan can be avoided through the use of the inventive method. A total avoidance of activation of the engine fan can probably not be reached for all routes. However, the inventive method can be implemented as far as possible. It is possible to complete the method with limit values for acceleration, vehicle speed, etc. which must not be exceeded and/or under passed, wherein the inventive method is implemented until the extent that one of the limit values is reached.
The method is especially effective for utility vehicles, which usually have high power engines and thereby also have a bigger engine fan, to provide a sufficient airflow over the heat exchanger.